In this section, the rich literature on photonic reservoir implementations is categorized and briefly summarized. An alternative discussion on this specific area can be found in [1]}. Reviews on topics related to photonic spike processing [2]} and photonics for neuromorphic applications [3]} have also been published recently. In this review, optical reservoirs are categorized as spatially distributed array reservoirs (Sec. REF ) and reservoirs with delay feedback (Sec. REF ). On this last category, a detailed tutorial has recently been published [4]}.
